1. Field of the Invention
The present invention relates to a droplet discharging head and an image forming apparatus.
2. Description of the Related Art
Recently, ink-jet printers are required to have a high-speed and high quality printing performance and also required to be smaller, space-saving, and lower price. Thus, it is necessary for a droplet discharging head, which is a main component of the ink-jet printer, to be highly integrated and smaller. Therefore, a technique to apply a Micro Electro-Mechanical System (MEMS) method to droplet discharging heads has been developed.
In particular, the MEMS method has been applied to a unimorph type droplet discharging head using a piezoelectric actuator because the unimorph type droplet discharging head can provide a high drive force by a thin film piezoelectric material, simple electrodes and a diaphragm (see Patent Documents 1 to 4, for example).
However, as will be explained later in detail with reference to FIG. 3, there has been a problem in that a space may be generated between a support substrate and a passage substrate depending on the shape of lead wirings or the amount of an adhesive agent due to a wiring step of the lead wirings. Then, if a sealing material, air, water or the like enters into a vibration room for a piezoelectric actuator, the performance of the piezoelectric actuator may be lowered.
For example, in Patent Document 2, a technique is disclosed in which a protection substrate is provided with a concave housing portion for housing an adhesive agent at a region facing a portion between lead electrodes at an adhering surface that is adhered to the lead electrodes.
Further, for example, in Patent Document 3, a method is disclosed in which a passage substrate and a sealing substrate are adhered with each other by an adhesive agent including particle insulating objects. It is said that the amount of the adhesive agent that flows out is regulated by the insulating objects.
By the technique disclosed in Patent Document 2, the adhesive agent is only introduced into the concave housing portion and generation of such a space as described above cannot be sufficiently suppressed. Thus, when the space is generated due to a step of the lead electrodes, the sealing material, air, water or the like cannot be prevented from entering into the vibration room for the piezoelectric actuator.
Further, in Patent Document 3, generation of the space between the passage substrate and the sealing substrate is not recognized and generation of the space cannot be sufficiently suppressed. Thus, the sealing material, air, water or the like cannot be prevented from entering into the vibration room for the piezoelectric actuator. Further, as there is a large limitation in the adhesive agent, it is difficult to make the thickness of the adhesive agent thin. Thus, there is a problem in improving rigidity that is necessary for driving the droplet discharging head at a high-speed.